Chinese contemporary artist Ai Weiwei never has limited himself to one medium. The 60-year-old has produced powerful sculptures, installations, photographs, videos and a stream of social-media postings as performance art and political statement.
Ai's heartbreaking documentary, "Human Flow," about the global refugee crisis, continues a tradition of making work that is pungent conceptually and aesthetically.
Shot in 23 countries and culled from 900 hours of footage of refugees from the Middle East, Africa, Mexico and elsewhere,the film avoids the tropes of most documentaries, using on-screen facts and figures sparingly or in the margins and narration not at all.
"News crawls," featuring headlines from PBS, The New York Times and other journalism outlets, creep across the screen, adding minimal context and contrasting sharply with fragments of poetry.
If at times it is not immediately clear which of the 40 refugee encampments Ai visited we are looking at - Greece? Kenya? Italy? The West Bank? - or who is on-screen, that's part of his point.
In place of talking-head interviews that might lend clarity, Ai's signature shot seems to be the overhead drone sequence, offering breathtaking bird's-eye views of, say, a refugee-packed boat on the open sea or an expanse of cubicle-like shelters inside a massive airplane hangar.
Aestheticizing the tragic does not undercut it, but rather reinforces it.
In other scenes, Ai turns his unblinking camera on an individual, forcing the audience to confront, over an uncomfortably long time, our common humanity with those who are, all too often, rendered as statistics.
At nearly 2½ hours, the film is long, and it sags here and there, yet the cumulative effect is not exhaustion or boredom, but sorrow and outrage at the violence, poverty and persecution - religious, ethnic or political - that have driven these people from their homes.
At a couple of points, Ai turns his gaze from humanity to focus on an animal. One wordless sequence features a cow limping unsteadily down an unidentified street. Another segment details the herculean effort and expense undertaken, in 2016, to relocate a single tiger from a zoo in Gaza to the South African wild. At these times, by deliberately playing on our sympathy for nonhuman suffering, "Human Flow" asks us, implicitly, why we seem to care so much about certain living creatures and not others.